Brush cleaning apparatus, chemical-mechanical polishing (cmp) system and wafer processing method

ABSTRACT

A method of processing a wafer is disclosed. The method includes, in some embodiments, causing a relative movement between a cleaning brush and a wafer. During the relative movement, a planar cleaning surface of the cleaning brush is brought into contact with a surface of the wafer to remove contaminants from the surface of the wafer. A first size of the cleaning brush, in a plan view, is larger than a second size of the wafer in the plan view.

REFERENCE TO RELATED APPLICATION

This Application is a Divisional of U.S. application Ser. No. 14/105,242filed on Dec. 13, 2013, the contents of which are hereby incorporated byreference in their entirety.

BACKGROUND

During a manufacturing process of semiconductor devices, variousfeatures are sequentially formed on a wafer resulting in an increasinglynon-planar surface of the wafer. Such a non-planar surface is planarizedto improve quality and/or uniformity of features subsequently formed onthe wafer. Chemical mechanical polishing (CMP) is a wafer processingtechnique that is used to planarize surfaces of wafers. A CMP processremoves excess materials, such as dielectric and/or conductive layers,from a surface of a wafer. The planarization operation leavescontaminants, such as residues of the removed materials, on theplanarized surface. A brush cleaning operation is performed to removesuch contaminants from the planarized surface, readying the wafer forsubsequent processing.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout. The drawings are not to scale, unless otherwisedisclosed.

FIG. 1 is a schematic block diagram of a CMP system in accordance withsome embodiments.

FIG. 2A is a schematic top view and FIG. 2B is a schematic side view ofa brush cleaning apparatus in accordance with some embodiments.

FIGS. 2C-2D are schematic side views of various brush cleaningapparatuses in accordance with some embodiments.

FIGS. 3A and 3B are schematic side views of various brush cleaningapparatuses in accordance with some embodiments.

FIG. 4A is a schematic side view of a cleaning brush in accordance withsome embodiments.

FIGS. 4B-4D are schematic top views of various cleaning brushes inaccordance with some embodiments.

FIG. 5A is a schematic side view and FIG. 5B is a schematic top view ofa cleaning brush in accordance with some embodiments.

FIG. 5C is a schematic side view and FIG. 5D is a schematic top view ofa cleaning brush in accordance with some embodiments.

FIG. 5E is a schematic side view and FIG. 5F is a schematic top view ofa cleaning brush in accordance with some embodiments.

FIG. 6 is a flow chart of a brush cleaning process in accordance withsome embodiments.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. An inventiveconcept may; however, be embodied in many different forms and should notbe construed as being limited to the embodiments set forth herein. Itwill be apparent; however, that one or more embodiments may be practicedwithout these specific details.

In some embodiments, a brush cleaning operation includes bringing aplanar cleaning surface of at least one cleaning brush into contact witha surface of a wafer, during a relative movement between the cleaningbrush and the wafer, to remove contaminants from the wafer surface. Theplanar cleaning surface contacts the wafer surface in a surface contact,permitting a relatively wide area, in at least one embodiment, theentire area, of the wafer surface to be brushed at the same time.Compared to other approaches where a rotating roller is used as thecleaning brush and contacts the wafer in a line contact, the brushcleaning operation in accordance with some embodiments provides a widercontact area and greater cleaning efficiency.

FIG. 1 is a schematic block diagram of a CMP system 100 in accordancewith some embodiments. The CMP system 100 includes a bulk polisher 110,a buff polisher 120, a brush cleaning apparatus 130, a pencil cleaningapparatus 140, and a drying apparatus 150 arranged sequentially along aprocess line 160.

The bulk polisher 110 is configured to reduce a thickness of a wafer. Insome embodiments, the bulk polisher 110 includes a rotatable polishingpad, one or more nozzles for dispensing a CMP slurry on the polishingpad, and a carrier head configured to hold the wafer with the wafersurface to be planarized facing the polishing pad. In a bulk polishingoperation, the polishing pad is rotated, the carrier head presses thewafer surface to be planarized against the rotating polishing pad, andthe CMP slurry is dispensed on the polishing pad. The CMP slurry helpsto remove material from the wafer surface through a combination ofchemical and/or mechanical actions. In at least one embodiment, the CMPslurry chemically reacts with the material to be removed to soften ordissolute the material. In at least one embodiment, the CMP slurryincludes abrasive particles to increase the mechanical grinding effect.An average thickness reduction of the wafer during a polishing operationdivided by the duration of the polishing operation is referred to as theremoval rate. The removal rate of the bulk polishing operation performedby the bulk polisher 110 depends on a number of factors including, butnot limited to, the hardness of the polishing pad, the pressure withwhich the wafer surface is pressed against the polishing pad, the CMPslurry composition, the relative velocity between the wafer surface andthe polishing pad, and other like factors.

The buff polisher 120 is arranged downstream of the bulk polisher 110 inthe process line 160, and is configured to further reduce a thickness ofthe wafer at a removal rate lower than that of the bulk polisher 110. Insome embodiments, the buff polisher 120 includes elements similar tothose described with respect to the bulk polisher 110. To achieve aremoval rate lower than the bulk polisher 110, the buff polisher 120includes, in one or more embodiments, a softer polishing pad than thepolishing pad of the bulk polisher 110 and/or finer CMP slurry abrasiveparticles than used by the bulk polisher 110. Other arrangements arewithin the scope of various embodiments.

The bulk polisher 110 and buff polisher 120 are commonly referred to asa polishing apparatus 170, and the corresponding bulk polishingoperation and buff polishing operation are commonly referred to as apolishing operation. In at least one embodiment, the polishing apparatus170 includes more than one bulk polisher 110 and/or more than one buffpolisher 120. In at least one embodiment, the bulk polisher 110 or thebuff polisher 120 is omitted from the polishing apparatus 170, and thecorresponding bulk polishing operation or buff polishing operation isomitted from the polishing operation of the polishing apparatus 170. Inat least one embodiment, the polishing operation is performed on onesurface of the wafer. In at least one embodiment, the polishingoperation is performed on both opposite surfaces of the wafer.

The polishing operation removes a thickness of the wafer beingplanarized, but leaves contaminants on the wafer. Examples ofcontaminants include residues of the material being removed from thewafer, abrasive particles contained in the CMP slurry or dislodged fromthe polishing pad, particles formed by agglomeration of the CMP slurry,byproducts of the chemical reaction between the CMP slurry and thematerial of the wafer, other foreign matters, and like contaminants. Insome situations, contaminants are present on both surfaces of the wafereven if the polishing operation is performed on one of the surfaces.

The brush cleaning apparatus 130 is arranged downstream of the polishingapparatus 170 and configured to remove contaminants from the wafer in abrush cleaning operation. The brush cleaning apparatus 130 includes atleast one cleaning brush having a planar cleaning surface. In the brushcleaning operation, the planar cleaning surface is brought into contactwith a surface to be brush-cleaned of the wafer, during a relativemovement between the cleaning brush and the wafer, thereby removingcontaminants from the wafer surface. In at least one embodiment, thebrush cleaning apparatus 130 includes one or more nozzles configured tosupply at least one cleaning liquid to an interface between the wafersurface and the cleaning brush to improve the efficiency and/or qualityof the brush cleaning operation. In at least one embodiment, the brushcleaning apparatus 130 includes a pair of cleaning brushes forperforming the brush cleaning operation on both opposite surfaces of thewafer simultaneously. In some embodiments, the brush cleaning operationdoes not reduce a thickness of the wafer.

The pencil cleaning apparatus 140 is arranged downstream of the brushcleaning apparatus 130 and configured to remove contaminants remainingon the wafer surface(s) after the brush cleaning operation performed bythe brush cleaning apparatus 130. In some embodiments, the pencilcleaning apparatus 140 includes a pencil type cleaning elementconfigured to come into contact with the wafer surface during a relativemovement between the pencil type cleaning element and the wafer, toremove the remaining contaminants from the wafer surface. In at leastone embodiment, the pencil cleaning apparatus 140 includes one or morenozzles configured to dispense at least one cleaning liquid onto thewafer surface to improve the efficiency and/or quality of the pencilcleaning operation. In at least one embodiment, the pencil cleaningoperation is performed on one surface of the wafer. In at least oneembodiment, the pencil cleaning operation is performed on both oppositesurfaces of the wafer. In one or more embodiments, the pencil cleaningapparatus 140 is omitted from the CMP system 100.

The drying apparatus 150 is arranged downstream of the pencil cleaningapparatus 140, or downstream of the brush cleaning apparatus 130 whenthe pencil cleaning apparatus 140 is omitted. The drying apparatus 150is configured to dry the cleaning liquid(s) supplied to the wafer duringthe brush cleaning operation and/or the pencil cleaning operation. In atleast one embodiment, the drying apparatus 150 includes a spinning unitconfigured to dry the cleaned wafer in a spin drying operation. Otherarrangements for drying the cleaned wafer are within the scope ofvarious embodiments. In at least one embodiment, the drying apparatus150 further includes a rinsing unit configured to rinse the cleanedwafer, for example, with water, before drying the cleaned and rinsedwafer. The cleaned and dried wafer is further transferred downstream ofthe drying apparatus 150 along the process line 160 to subsequentprocessing.

FIG. 2A is a schematic top view and FIG. 2B is a schematic side view ofa brush cleaning apparatus 200 in accordance with some embodiments. Inat least one embodiment, the brush cleaning apparatus 200 corresponds tothe brush cleaning apparatus 130 in the CMP system 100 described withrespect to FIG. 1. However, the brush cleaning apparatus 200 is notlimited to CMP systems. For example, in one or more embodiments, thebrush cleaning apparatus 200 is configured to perform a brush cleaningoperation after a deep chemical vapor deposition (CVD) process.

As shown in FIG. 2A, the brush cleaning apparatus 200 includes a wafersupport 210, at least one cleaning brush 220, a cleaning brush movingmechanism 230, and at least one nozzle 240.

The wafer support 210 is configured to support a wafer 250 to bebrush-cleaned. The wafer support 210 includes a plurality of waferholding elements 212, 214, 216, 218 arranged around a peripheral edge ofthe wafer 250, and configured to hold the wafer 250 at the peripheraledge. In at least one embodiment, the wafer holding elements 212, 214,216, 218 include claws for holding the wafer 250 in a fixed positionrelative to the wafer support 210. In at least one embodiment, the waferholding elements 212, 214, 216, 218 include rollers for holding theperipheral edge of the wafer 250 while permitting the wafer 250 torotate relative to the wafer support 210. In some embodiments, the wafersupport 210 is configured to hold the wafer 250 stationary during abrush cleaning operation. In some embodiments, the wafer support 210 isconfigured to move the wafer 250, or permit the wafer 250 to move,during the brush cleaning operation. Other arrangements are within thescope of various embodiments.

The at least one cleaning brush 220 is configured to brush contaminantsoff a surface of the wafer 250. In at least one embodiment, the at leastone cleaning brush 220 includes one cleaning brush for brush-cleaningone surface of the wafer 250. In at least one embodiment, the at leastone cleaning brush 220 includes a pair of cleaning brushes forbrush-cleaning both opposite surfaces of the wafer 250. For example, asshown in FIG. 2B, the at least one cleaning brush 220 includes a pair ofcleaning brushes 220U, 220L arranged on opposite sides of the wafer 250,for brush-cleaning the corresponding opposite surfaces 252U, 252L of thewafer 250. For simplicity, the wafer support 210 and the cleaning brushmoving mechanism 230 are omitted from FIG. 2B.

The at least one cleaning brush 220 has a planar cleaning surfaceconfigured to come into contact with the wafer 250 supported by thewafer support 210 to remove contaminants from the wafer 250. Forexample, as shown in FIG. 2B, the cleaning brush 220U has, on a firstside facing the corresponding surface 252U of the wafer 250, a planarcleaning surface 222U configured to come into contact with the surface252U and remove contaminants from the surface 252U in a brush cleaningoperation. The cleaning brush 220U further has a second side (ornon-cleaning side) 224U opposite to the planar cleaning surface 222U.Similarly, the cleaning brush 220L has, on a first side facing thecorresponding surface 252L of the wafer 250, a planar cleaning surface222L configured to come into contact with the surface 252L and removecontaminants from the surface 252L in a brush cleaning operation. Thecleaning brush 220L further has a second side 224L opposite to theplanar cleaning surface 222L.

The cleaning brush moving mechanism 230 is configured to cause arelative movement between the at least one cleaning brush 220 and thewafer 250 supported by the wafer support 210. The cleaning brush movingmechanism 230 includes a robot arm 232 having opposite first and secondends 234, 236. The at least one cleaning brush 220 is rotatably attachedto the first end 234 of the robot arm 232, and is rotatable relative tothe first end 234. The robot arm 232 is pivotable about the second end236 to swing the at least one cleaning brush 220 across the wafer 250.The robot arm 232 and/or the at least one cleaning brush 220 is/arefurther moveable toward and away from the wafer support 210 in athickness direction (or a normal direction) of the wafer 250 supportedby the wafer support 210. In at least one embodiment, the robot arm 232is moveable translationally and/or rotationally relative to the wafersupport 210 in a plane parallel to the plane of the wafer 250 supportedby the wafer support 210. The cleaning brush moving mechanism 230includes one or more motors and/or hydraulic cylinders and/or otherdriving mechanisms to effect the described movements of the robot arm232 and/or the at least one cleaning brush 220. Other arrangements formoving the at least one cleaning brush 220 relative to the wafer 250 arewithin the scope of various embodiments.

The nozzle 240 is configured to supply at least one cleaning liquid tothe surface contact between the at least one cleaning brush 220 and thewafer 250. Example cleaning liquids include, but are not limited to,water, deionized (DI) water, and one or more chemicals such as NH₄OH, HFand the like. In at least one embodiment, the cleaning liquid suppliedby the nozzle 240 dislodges contaminants from the wafer surface and thedislodged contaminants are brushed off by the at least one cleaningbrush 220. In at least one embodiment, the cleaning liquid furthermaintains an intended wetness at the contact between the at least onecleaning brush 220 and the wafer 250, to reduce abrasive damage to thewafer surface.

In a brush cleaning operation, the cleaning brush moving mechanism 230causes a relative movement between the at least one cleaning brush 220and the wafer 250 supported by the wafer support 210. During therelative movement between the at least one cleaning brush 220 and thewafer 250, the planar cleaning surface of the at least one cleaningbrush 220 is brought into contact with the wafer surface to bebrush-cleaned. As a result, contaminants are brushed off the wafersurface by the surface contact between the planar cleaning surface andthe wafer surface. Compared to other approaches where a rotating rolleris used as the cleaning brush and contacts the wafer in a line contact,the brush cleaning operation in accordance with some embodimentsprovides a wider contact area and greater cleaning efficiency. Inaddition, potential cleaning defects due to unbalance or shifting of therotating roller in the other approaches are avoidable in someembodiments, because the surface contact between the cleaning brush andthe wafer in some embodiments is more stable than the line contactbetween the rotating roller and the wafer in the other approaches.

In the specifically disclosed embodiment shown in FIG. 2A, the shape ofthe at least one cleaning brush 220 is circular. However, such acircular shape is an example and does not affect the brush cleaningoperation in one or more embodiments, especially when the at least onecleaning brush 220 is rotated during the brush cleaning operation. Othershapes of the at least one cleaning brush 220 are within the scope ofvarious embodiments.

In some embodiments, the planar cleaning surface of the at least onecleaning brush 220 and the plane of the wafer 250 are oriented in adirection between the vertical direction and the horizontal direction.In at least one embodiment, the planar cleaning surface of the at leastone cleaning brush 220 and the plane of the wafer 250 are orientedvertically to be perpendicular to the ground surface. In at least oneembodiment, the planar cleaning surface of the at least one cleaningbrush 220 and the plane of the wafer 250 are oriented horizontally to beparallel to the ground surface.

In some embodiments, the at least one cleaning brush 220 includes aporous material defining the planar cleaning surface. For example, thecleaning brush 220U includes a porous material defining the planarcleaning surface 222U and/or the cleaning brush 220L includes a porousmaterial defining the planar cleaning surface 222L. Example porousmaterials for the planar cleaning surfaces include, but are not limitedto, one or more of polyvinyl alcohol (PVA), polyamide (PA), polyurethane(PU), polybutylene terephthalate (PBT), and polyethylene terephthalate(PET). Such porous materials are selected in one or more embodiments fortheir softness which permits contaminants to be brushed off withoutdamaging the wafer surface. The porous material in one or moreembodiments further functions as a sponge for holding, and/or as amedium for transferring, the cleaning liquid as described herein. Thecleaning liquid keeps the contact between the planar cleaning surfaceand the wafer surface at an intended wetness, improves the cleaningefficiency and reduces potential abrasive damage to the wafer surface.

In some embodiments, the porous material has a porosity in range from 5%to 80%. In at least one embodiment, the porosity of the porous materialis determined at a surface or a cross-section of the porous material.The total area of all pores in a region of the surface or cross-sectionof the porous material is determined. The total area of the region isdetermined. The porosity of the porous material is determined as a ratioof the total area of all pores in the region at the surface orcross-section to the total area of the region. When the porosity of theporous material is lower than 5%, the mount of cleaning liquid holdableand/or transferrable by the porous material is potentially insufficientfor maintaining an intended wetness at the contact between the planarcleaning surface and the wafer surface, thereby potentially reducingcleaning efficiency and/or causing damage to the wafer surface. When theporosity of the porous material is higher than 80%, the contact areabetween the planar cleaning surface and the wafer surface is potentiallyinsufficient to provide an intended cleanliness which depends on boththe presence of the cleaning liquid at, and the area of, the contactbetween the planar cleaning surface and the wafer surface. In at leastone embodiment, the porosity of the porous material ranges from 20% to60%.

In some embodiments, the porous material has a pore size in range from 5um to 200 um. In at least one embodiment, the pore size of the porousmaterial is determined at a surface or a cross-section of the porousmaterial. An average diameter of all pores in a region of the surface orcross-section of the porous material is determined as the pore size ofthe porous material. When the pore size of the porous material is lowerthan 5 um, the mount of cleaning liquid holdable and/or transferrable bythe porous material is potentially insufficient for maintaining anintended wetness at the contact between the planar cleaning surface andthe wafer surface, thereby potentially reducing cleaning efficiency.When the pore size of the porous material is higher than 200 um, acleaning quality and/or mechanical strength of the cleaning brush is/arepotentially insufficient. In at least one embodiment, the pore size ofthe porous material ranges from 30 um to 150 um.

In some embodiments, a size of the cleaning brush in plan view (i.e.,when seen in the direction normal to the wafer surface) is smaller thana size of the wafer in plan view. For example, the size of the cleaningbrush 220U or 220L in FIG. 2B is smaller than the size of the wafer 250.In some embodiments, the size of the cleaning brush in plan view isequal to the size of the wafer in plan view. For example, the size ofthe cleaning brush 220U or 220L in FIG. 2C is equal to the size of thewafer 250. In some embodiments, the size of the cleaning brush in planview is greater than the size of the wafer in plan view. For example,the size of the cleaning brush 220U or 220L in FIG. 2D is greater thanthe size of the wafer 250. In some embodiments, the sizes of the planarcleaning surfaces 222U are 222L are different from each other. Forexample, in at least one embodiment, the size of the cleaning brush 220Uis greater than the size of the wafer 250 which, in turn, is greaterthan the size of the cleaning brush 220L.

In some embodiments, the size of the cleaning brush in plan view is in arange from 0.55 to 1.5 times of the size of the wafer in plan view. Asthe size of the cleaning brush becomes smaller compared to the size ofthe wafer, the at least one cleaning brush 220 moves over a longerperiod and/or a greater distance to clean the wafer surface of the wafer250 which, in turn, results in a longer brush cleaning operation and/orconsumes a greater amount of the cleaning liquid. When the size of thecleaning brush is smaller than 0.55 times of the size of the wafer, thelength of the brush cleaning operation and/or the amount of consumedcleaning liquid per brush cleaning operation potentially reach a levelthat significantly affects the efficiency of the brush cleaningoperation.

As the size of the cleaning brush becomes greater compared to the sizeof the wafer, the at least one cleaning brush 220 moves over a shorterperiod and/or a shorter distance to clean the wafer surface of the wafer250 which, in turn, results in a shorter brush cleaning operation and/orconsumes a smaller amount of the cleaning liquid. When the size of thecleaning brush is equal or greater than the size of the wafer, as shownin FIGS. 2C-2D, some embodiments eliminate a relative translationalmovement between the at least one cleaning brush 220 and the wafer 250,and maintain a relative rotational movement therebetween, therebyreducing power consumption. However, when the size of the cleaning brushis greater than 1.5 times of the size of the wafer, there is a potentialdifficulty in mechanical handling and/or movement of such a large sizecleaning brush. In at least one embodiment, the size of the cleaningbrush ranges from 0.6 times to 1.2 times the size of the wafer.

In some embodiments, the relationship between the size of the cleaningbrush and the size of the wafer is a factor to be considered inarranging one or more nozzles for supplying one or more cleaning liquidsfor the brush cleaning operation.

FIG. 3A is a schematic side view of a brush cleaning apparatus 300A inaccordance with some embodiments. For simplicity, the wafer support andthe cleaning brush moving mechanism are omitted from FIG. 3A. The brushcleaning apparatus 300A include a plurality of nozzles 342, 344, 346,348 corresponding to the nozzle 240 described with respect to FIG. 2A.

In the brush cleaning apparatus 300A, the cleaning brushes 220U and 220Lare smaller than the wafer 250. As a result, the nozzles 342, 344directed at an area of the wafer 250 not obstructed by the cleaningbrushes 220U and 220L are used in one or more embodiments to directlysupply the corresponding one or more cleaning liquids to thecorresponding surfaces of the wafer 250. The supplied cleaning liquid isbrought to the contact between the wafer 250 and the planar cleaningsurfaces 222U, 222L by relative movements between the at least onecleaning brush 220 and the wafer 250.

In one or more embodiments, the nozzles 346, 348 are used in addition toor in lieu of the nozzles 342, 344 to indirectly supply thecorresponding one or more cleaning liquids to the corresponding surfacesof the wafer 250. The nozzles 346, 348 are directed at the non-cleaningsides 224U, 224L of the corresponding cleaning brushes 220U and 220Lwhich are opposite to the planar cleaning surfaces 222U, 222L. Thecleaning liquid(s) supplied to the non-cleaning sides 224U, 224L is/aretransferred through the porous material of the corresponding cleaningbrushes 220U and 220L to the corresponding planar cleaning surfaces222U, 222L.

FIG. 3B is a schematic side view of a brush cleaning apparatus 300B inaccordance with some embodiments. For simplicity, the wafer support andthe cleaning brush moving mechanism are omitted from FIG. 3B. The brushcleaning apparatus 300B include the nozzles 346, 348.

In the brush cleaning apparatus 300B, the cleaning brushes 220U and 220Lhave a size about equal to or greater than that of the wafer 250. As aresult, the wafer surfaces of the wafer 250 are substantially covered bythe cleaning brushes 220U and 220L and it is difficult to directlysupply one or more cleaning liquids to the surfaces to be brush-cleanedof the wafer 250. The nozzles 342, 344 described with respect to thebrush cleaning apparatus 300A are omitted, or provided but not used, inthe brush cleaning apparatus 300B. The brush cleaning apparatus 300Buses the nozzles 346, 348 to indirectly supply one or more cleaningliquids to the corresponding surfaces of the wafer 250 via the porousmaterial of the cleaning brushes 220U and 220L, as described withrespect to FIG. 3A.

In some embodiments, the transfer of cleaning liquid through thecleaning brush is enhanced by forming holes extending through thecleaning brush.

FIG. 4A is a schematic side view of a cleaning brush 420 in accordancewith some embodiments. In at least one embodiment, the cleaning brush420 corresponds to the at least one cleaning brush 220, the cleaningbrush 220U or the cleaning brush 220L as described herein.

The cleaning brush 420 is formed of a porous material, and has a planarcleaning surface 422 and an opposite non-cleaning side 424. The cleaningbrush 420 further includes a plurality of holes 425 extending throughthe cleaning brush 420, from the non-cleaning side 424 to the planarcleaning surface 422. Example opening shapes of the holes 425 include,but are not limited to, circle, triangle, square, and other like shapes.In one or more embodiments, the holes 425 have straight sidewallsbetween the openings on the opposite sides 422, 424 of the cleaningbrush 420. In one or more embodiments, the holes 425 extendperpendicular to a plane of the cleaning brush 420. An example method offorming the holes 425 includes laser drilling. A cleaning liquiddispensed by the nozzle 348 on the non-cleaning side 424 is transferredto the planar cleaning surface 422 via both the porous material of thecleaning brush 420 and the holes 425. As a result, the cleaning liquidtransfer efficiency and/or the cleaning efficiency is/are increased.

In some embodiments, the holes 425 have an average hole size in a rangefrom 0.5 mm to 2 mm.

In some embodiments, adjacent holes among the holes 425 are arranged atan edge-to-edge pitch in a range from 2 to 4 times of the average holesize.

When the average hole size is smaller than 0.1 mm and/or the pitchbetween adjacent holes 425 is greater than 5 times of the average holesize, the amount of cleaning liquid transferred via the holes 425 andone or more positive effects associated therewith is/are limited. Whenthe average hole size is greater than 2.5 mm and/or the pitch betweenadjacent holes 425 is less than 2 times of the average hole size, theamount of cleaning liquid transferred via the holes 425 potentiallybecomes excessive, which results in potential waste of cleaning liquid.

FIGS. 4B-4D are schematic top views of various cleaning brushes, showingvarious arrangements of holes 425 in accordance with some embodiments.As shown in FIG. 4B, the holes 425 are arranged along diametrical lines426 in one or more embodiments. As shown in FIG. 4C, the holes 425 arearranged along concentric circles 427 in one or more embodiments. Asshown in FIG. 4D, the holes 425 are arranged along a plurality ofcolumns 428 and a plurality of rows 429 in one or more embodiments. Thearrangements shown in FIGS. 4B-4D are examples. Other arrangementsand/or combinations of the described arrangements are within the scopeof various embodiments.

FIG. 5A is a schematic side view and FIG. 5B is a schematic top view ofa cleaning brush 520A in accordance with some embodiments. In at leastone embodiment, the cleaning brush 520A corresponds to the at least onecleaning brush 220, the cleaning brush 220U or the cleaning brush 220Las described herein.

The cleaning brush 520A includes a porous material 560 defining a planarcleaning surface 522, and a core material 570 defining the non-cleaningside 524. The porous material 560 is attached to the core material 570.Example techniques for attaching the porous material 560 to the corematerial 570 include, but are not limited to, adhesive, heat bonds,co-molding, coating and other like techniques. In at least oneembodiment, the core material 570 is mechanically and/or chemicallystronger than the porous material 560 to improve robustness and/orservice life of the cleaning brush 520A. In one or more embodiments, thecore material 570 is a non-porous material. Example materials of thecore material 570 include, but are not limited to, at least one ofpolypropene (PP), polythene (PE), and polyvinyl chloride (PVC). In thespecifically disclosed embodiment shown in FIGS. 5A-5B, the size of thecore material 570 in plan view is larger than that of the porousmaterial 560. However, such an arrangement is an example. Otherarrangements are within the scope of various embodiments. For example,in one or more embodiments, the size of the core material 570 is equalto the size of the porous material 560.

FIG. 5C is a schematic side view and FIG. 5D is a schematic top view ofa cleaning brush 520C in accordance with some embodiments. In at leastone embodiment, the cleaning brush 520C corresponds to the at least onecleaning brush 220, the cleaning brush 220U or the cleaning brush 220Las described herein.

The cleaning brush 520C is similar to the cleaning brush 520A, exceptthat the cleaning brush 520C additionally includes a plurality of holes525 extending through the porous material 560 and the core material 570,from the non-cleaning side 524 to the planar cleaning surface 522. Insome embodiments, the holes 525 correspond to the holes 425 as describedherein. For example, as shown in FIG. 5D, the holes 525 are arranged inconcentric circles 527. The holes 525 function to transfer a cleaningliquid dispensed on the non-cleaning side 524 to the planar cleaningsurface 522, as described herein with respect to the holes 425.

FIG. 5E is a schematic side view and FIG. 5F is a schematic top view ofa cleaning brush 520E in accordance with some embodiments. In at leastone embodiment, the cleaning brush 520C corresponds to the at least onecleaning brush 220, the cleaning brush 220U or the cleaning brush 220Las described herein.

The cleaning brush 520E is similar to the cleaning brush 520C, exceptthat the porous material 560 is omitted. The planar cleaning surface 522is defined by the core material 570. In at least one embodiment, thecore material 570 includes a non-porous material. A cleaning liquid isheld in or transferred through the holes 525 of the cleaning brush 520Eas described herein.

FIG. 6 is a flow chart of a brush cleaning process 600 in accordancewith some embodiments. In at least one embodiment, the brush cleaningprocess 600 is performed by the brush cleaning apparatus 200 using oneor more of the cleaning brushes described with respect to FIGS. 2A-5F.

At operation 605, a relative movement is caused between a cleaning brushand a wafer. For example, a cleaning brush moving mechanism 230 isoperated to cause a relative translational and/or rotational movementbetween a cleaning brush 220U and/or 220L and a wafer 250, as describedwith respect to FIGS. 2A-2B.

At operation 615, during the relative movement between the cleaningbrush and the wafer, a planar cleaning surface of the cleaning brush isbrought into contact with a surface of the wafer to remove contaminantsfrom the surface of the wafer. For example, during the relative movementbetween the cleaning brush 220U and/or 220L and the wafer 250, a planarcleaning surface 222U or 222L of the cleaning brush 220U and/or 220L isbrought into contact with the corresponding surface 252U and/or 252L ofthe wafer 250 to remove contaminants from the 252U and/or 252L of thewafer 250, as described with respect to FIGS. 2A-2B.

At operation 625, at least one cleaning liquid is supplied directly tothe surface of the wafer and/or via the cleaning brush. For example, acleaning liquid is supplied directly to the surface of the wafer 250from the nozzles 342, 344, as described with respect to FIG. 3A.Alternatively or additionally, a cleaning liquid is supplied to thesurface of the wafer 250 from the nozzles 346, 348 and through thecleaning brush 220U and/or 220L, as described with respect to FIGS.3A-3B. In some embodiments, operation 625 is omitted.

One or more effects discussed with respect to the brush cleaningapparatus and cleaning brushes described in reference to FIGS. 2A-5Fis/are achievable by the brush cleaning process 600 in accordance withsome embodiments.

The above method(s) include(s) example operations, but the operations insome embodiments are not performed in the order shown. Operations may beadded, replaced, changed order, and/or eliminated as appropriate, inaccordance with the spirit and scope of embodiments of the disclosure.Embodiments that combine different features and/or different embodimentsare within the scope of the disclosure and will be apparent to those ofordinary skill in the art after reviewing this disclosure.

According to some embodiments, a brush cleaning apparatus comprises awafer support configured to support a wafer, and at least one cleaningbrush moveable relative to the wafer support. The at least one cleaningbrush has opposite first and second sides, and, on the first side, aplanar cleaning surface configured to come into contact with the wafersupported by the wafer support to remove contaminants from the wafer.

According to some embodiments, a chemical-mechanical polishing (CMP)system comprises a polishing apparatus configured to reduce a thicknessof a wafer, and a brush cleaning apparatus arranged downstream of thepolishing apparatus. The brush cleaning apparatus comprises a pair ofcleaning brushes configured to face and move relative to oppositesurfaces of the wafer. The cleaning brushes have planar cleaningsurfaces configured to come into contact with the corresponding surfacesof the wafer to remove contaminants from the surfaces of the wafer.

In a method of processing a wafer, a relative movement is caused betweena cleaning brush and a wafer. During the relative movement, a planarcleaning surface of the cleaning brush is brought into contact with asurface of the wafer to remove contaminants from the surface of thewafer. A size of the cleaning brush, in plan view, is in a range from0.55 to 1.5 times of a size of the wafer in plan view.

It will be readily seen by one of ordinary skill in the art that one ormore of the disclosed embodiments fulfill one or more of the advantagesset forth above. After reading the foregoing specification, one ofordinary skill will be able to affect various changes, substitutions ofequivalents and various other embodiments as broadly disclosed herein.It is therefore intended that the protection granted hereon be limitedonly by the definition contained in the appended claims and equivalentsthereof.

What is claimed is:
 1. A method of processing a wafer, the methodcomprising: causing a relative movement between a cleaning brush and awafer; during the relative movement, bringing a planar cleaning surfaceof the cleaning brush into contact with a surface of the wafer to removecontaminants from the surface of the wafer; and wherein a first size ofthe cleaning brush, in a plan view, is greater than or equal to a secondsize of the wafer in the plan view.
 2. The method of claim 1, furthercomprising: bringing a plurality of discrete wafer holding elements intocontact with spatially separated points along a peripheral edge of thewafer, wherein the plurality of discrete wafer holding elements areconfigured to hold the wafer in a fixed position during the relativemovement between the cleaning brush and the wafer.
 3. The method ofclaim 1, wherein the planar cleaning surface is defined by a layer ofporous material.
 4. The method of claim 3, wherein the layer of porousmaterial has a porosity in a range from 5% to 80%.
 5. The method ofclaim 3, wherein the cleaning brush comprises a layer of core materialcoupled to the layer of porous material, the layer of core materialhaving a flat surface facing away from the layer of porous material. 6.The method of claim 5, further comprising: applying a cleaning liquid tothe flat surface of the layer of core material; and transferring thecleaning liquid from the flat surface of the layer of core material,through the layer of porous material, and to the planar cleaningsurface.
 7. The method of claim 5, wherein interior sidewalls of thelayer of core material and the layer of porous material are alignedalong lines that are perpendicular to the planar cleaning surface todefine a plurality of holes respectively extending completely throughthe layer of core material and the layer of porous material.
 8. Themethod of claim 7, wherein the plurality of holes are arranged alongdiametrical lines extending outward from a center of the planar cleaningsurface.
 9. The method of claim 7, wherein the plurality of holescomprise a first plurality of holes arranged along a plurality ofcolumns extending in a first direction and a second plurality of holesarranged along a plurality of rows extending in a second direction thatis perpendicular to the first direction.
 10. The method of claim 1,further comprising: performing a bulk polishing operation to reduce athickness of the wafer at a first rate; performing a buff polishingoperation after the bulk polishing process is completed, wherein thebuff polishing operation further reduces the thickness of the wafer at asecond rate that is lower than the first rate; causing the relativemovement between the cleaning brush and the wafer after the buffpolishing operation is completed; and performing a pencil cleaningoperation to remove contaminants from the wafer after the relativemovement between the cleaning brush and the wafer is completed.
 11. Amethod of cleaning a substrate, comprising: bringing a planar cleaningsurface of a cleaning brush into contact with a surface of a substrateto remove contaminants from the surface of the substrate, wherein theplanar cleaning surface is defined by a porous material; applying acleaning liquid to a back-side of the cleaning brush, wherein theback-side of the cleaning brush opposes the planar cleaning surface; andtransferring the cleaning liquid from the back-side of the cleaningbrush, through the porous material, and to the planar cleaning surface.12. The method of claim 11, wherein the cleaning brush is rotatablyattached to a robot arm; and wherein the robot arm is configured to movethe cleaning brush relative to the substrate by operating a cleaningbrush moving mechanism coupled to the robot arm, the cleaning brushmoving mechanism including one or more hydraulic cylinders.
 13. Themethod of claim 11, wherein a ratio of a total area of pores in a regionof the planar cleaning surface to a total area of the region of theplanar cleaning surface is in a range from 20% to 80%.
 14. The method ofclaim 11, wherein a first diameter of the cleaning brush is larger thana second diameter of the substrate.
 15. The method of claim 11, whereinthe cleaning brush comprises a core material contacting a back-side ofthe porous material that opposes the planar cleaning surface; andwherein interior sidewalls of the core material and the porous materialare aligned along lines that are perpendicular to the planar cleaningsurface to define a plurality of holes respectively extending completelythrough the core material and the porous material.
 16. The method ofclaim 11, wherein the porous material comprises polyethyleneterephthalate.
 17. A method of cleaning a substrate, comprising:bringing a plurality of discrete substrate holding elements into contactwith a peripheral edge of a substrate; bringing a planar cleaningsurface of a cleaning brush into contact with a surface of thesubstrate, wherein the planar cleaning surface is defined by a porousmaterial having a porosity in a range from 5% to 80%; providing acleaning liquid to the planar cleaning surface of the cleaning brush;and moving the planar cleaning surface relative to the substrate. 18.The method of claim 17, wherein the cleaning brush comprises a corematerial coupled to a back-side of the porous material opposing theplanar cleaning surface; and wherein a first diameter of the corematerial is equal to a second diameter of the porous material.
 19. Themethod of claim 18, wherein interior sidewalls of the core material andthe porous material are aligned along lines that are perpendicular tothe planar cleaning surface to define a plurality of holes respectivelyextending completely through the core material and the porous material,the plurality of holes formed by laser drilling.
 20. The method of claim17, further comprising: applying the cleaning liquid to a back-side ofthe cleaning brush, wherein the back-side of the cleaning brush opposesthe planar cleaning surface; and transferring the cleaning liquid fromthe back-side of the cleaning brush to the planar cleaning surface.